cancellation of my contract

Well for the past 4 months I've been trying to cancel my contract with mtn,I went to their branches at the malls,I was instructed to call 808 for a cancellation. The phone rings with no answer,I then decided to send them an e-mail but still no reply. They sent an sms telling me to pay for services I don't need anymore,I will not pay anything until I speak to someone and cancel that contract. Had I wanted an upgrade they would've assisted me with the speed of light.My cellphone number ********** 688